So far, it's just a one-off in a
classic VW Beetle. And apparently, they're
more efficient than gas/electric hybrids!
Hydraulic hybrids operate basically the same way as gasoline-electric hybrids, but they use a motor-pump instead of an electric motor-generator—and an accumulator rather than the battery pack. An accumulator is essentially a pressure tank that stores compressed gas or liquid. When the driver slows down or brakes, the pump forces the hydraulic fluid out of a low-pressure tank into a twin high-pressure tank. To accelerate, the fluid is forced back to the low-pressure tank past the pump/motor, which applies torque to the wheels. The hydraulic regenerative braking system, which can put as much as 80 percent of the braking energy back to the wheel, is more efficient than regen braking in current hybrid cars.
Take
that Detroit!
